Method for producing superheavy oil emulsion fuel

ABSTRACT

The method for producing a superheavy oil emulsion fuel includes the steps of (a) adding to a superheavy oil 0.1 to 0.6 parts by weight of a nonionic surfactant having an HLB (hydrophilic-lipophilic balance) of 13 to 19, based on 100 parts by weight of the superheavy oil, and water, to prepare a homogeneous liquid mixture; and (b) mechanically mixing the homogeneous liquid mixture with a high shearing stress, to produce a superheavy oil emulsion fuel having a particle size distribution. In this method, a 10% cumulative particle size is from 1.5 to 8 μm, a 50% cumulative particle size is from 11 to 30 μm, and a 90% cumulative particle size is from 25 to 150 μm, and coarse particles having particle sizes of 150 μm or more occupy 3% by weight or less in the entire emulsion fuel, and the concentration of the superheavy oil is from 76.5 to 82.0% by weight.

This application claims the benefit under 35 U.S.C. §371 of prior PCTInternational Application No. PCT/JP96/01431 which has an Internationalfiling date of May 27, 1997 which designated the United States ofAmerica, the entire contents of which are hereby incorporated byreferences.

TECHNICAL FIELD

The present invention relates to a method for producing an oil-in-watertype, superheavy oil emulsion fuel which is usable as fuels forthermoelectric power generation.

BACKGROUND ART

It is well known that the superheavy oil emulsion fuels give stableemulsion fuels when used together with additives, such as emulsifiers,stabilizers, and fluidizing agents, and various excellent emulsifiers tobe used in emulsion fuel compositions have been developed (See JapanesePatent Laid-Open No. 1-185394, U.S. Pat. No. 5,024,676, and JapanesePatent Laid-Open No. 1-313595). However, even when these additivesincluding emulsifiers, stabilizers, and fluidizing agents are used, theconcentration of the superheavy oil in the superheavy oil emulsion fuelis at most 77% by weight. A superheavy oil emulsion fuel which is stableand has good fluidity is easy to handle. As the concentration of thesuperheavy oil increases, the thermal energy loss by water decreases,thereby making the resulting emulsion fuel more valuable. Also, a highsuperheavy oil concentration is beneficial because it can be dilutedupon use where necessary.

DISCLOSURE OF THE INVENTION

In view of the above problems, an object of the present invention is toprovide a method for producing a stable, easy-to-handle superheavy oilemulsion fuel having a highly concentrated superheavy oil having goodfluidity.

Another object of the present invention is to provide a superheavy oilemulsion fuel obtainable by the above method.

Conventionally, it has been common to one skilled in the art that theparticle size distribution must be widened in order to produce highlyconcentrated emulsion fuels.

As a result of intensive research in view of solving the above problems,the present inventors have found that a stable emulsion can be obtainedat a superheavy oil concentration exceeding 77% by weight by limiting anamount of the superheavy oil in the emulsion to a particular range,limiting the kinds and amounts of the surfactants and an agitationstress to particular ranges, and limiting the particle size distributionto a given range. The present invention has been completed based uponthese findings.

Specifically, the present invention is concerned with the following:

(1) A method for producing a superheavy oil emulsion fuel comprising thesteps of:

(a) adding to a superheavy oil 0.1 to 0.6 parts by weight of a nonionicsurfactant having an HLB (hydrophilic-lipophilic balance) of 13 to 19,based on 100 parts by weight of the superheavy oil, and water, toprepare a homogeneous liquid mixture; and

(b) mechanically mixing the homogeneous liquid mixture with a highshearing stress, to produce a superheavy oil emulsion fuel having aparticle size distribution wherein a 10%-cumulative particle size isfrom 1.5 to 8 μm, a 50%-cumulative particle size is from 11 to 30 μm,and a 90%-cumulative particle size is from 25 to 150 μm, and whereincoarse particles having particle sizes of 150 μm or more occupy 3% byweight or less in the entire emulsion fuel, and wherein theconcentration of the superheavy oil is from 76.5 to 82.0% by weight;

(2) The method described in item (1) above, wherein an anionicsurfactant or cationic surfactant is further added in an amount so asnot to exceed the amount of the nonionic surfactant in step (a);

(3) The method described in item (1) or item (2) above, wherein apolymeric compound selected from the group consisting of naturallyoccurring polymers and synthetic polymers, or a water-swellable claymineral is further added in an amount so as not to exceed the amount ofthe nonionic surfactant in step (a);

(4) The method described in any one of items (1) to (3) above, whereinone or more compounds selected from the group consisting of oxides ofmagnesium, calcium, and iron, hydroxides of magnesium, calcium, andiron, and salts of magnesium, calcium, and iron are further added in anamount of 0.01 to 0.5 parts by weight, based on 100 parts by weight ofthe superheavy oil in step (a);

(5) The method described in any one of items (1) to (4) above, whereinthe mechanical mixing is carried out at a shearing stress of from 1,000to 20,000 s⁻¹ ;

(6) The method described in any one of items (1) to (5) above,subsequent to step (b), further comprising the step of:

(c) diluting the resulting mixture obtained in step (b) with water or asurfactant aqueous solution having an HLB of 13 to 19, to thereby adjustthe viscosity (100 s⁻¹, 25° C.) of the resulting mixture to 3000 cp orless;

(7) The method described in any one of items (1) to (6) above, whereinthe concentration of the superheavy oil is from 78.0 to 81.0% by weight;

(8) The method described in any one of items (1) to (7), wherein saidnonionic surfactant is an alkylene oxide adduct of an alkylphenol;

(9) The method described in item (2) above, wherein said anionicsurfactant is one or more compounds selected from the group consistingof lignin sulfonates, formalin condensates of lignin sulfonic acid andnaphthalenesulfonic acid or salts thereof, and formalin condensates ofnaphthalenesulfonates; and

(10) A superheavy oil emulsion fuel obtainable by the method describedin any one of items (1) to (9) above, wherein the superheavy oilemulsion fuel has a particle size distribution wherein a 10%-cumulativeparticle size is from 1.5 to 8 μm, a 50%-cumulative particle size isfrom 11 to 30 μm, and a 90%-cumulative particle size is from 25 to 150μm, and wherein coarse particles having particle sizes of 150 μm or moreoccupy 3% by weight or less in the entire emulsion fuel, and wherein theconcentration of the superheavy oil is from 76.5 to 82.0% by weight.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a particle size distribution of an emulsionfuel obtained in Example 1; and

FIG. 2 is a graph showing a particle size distribution of an emulsionfuel obtained in Comparative Example 1.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained in detail below.

The "superheavy oil" usable in the present invention refers to those ina solid or semi-fluid state at room temperature which do not flow unlessheated to a high temperature. Examples of the superheavy oils includethe following:

(1) Petroleum asphalts and mixtures thereof;

(2) Various treated products of petroleum asphalts, intermediates,residues, and mixtures thereof.

(3) High pour point-oils which do not even flow at high temperatures, orcrude oils;

(4) Petroleum tar pitches and mixtures thereof; and

(5) Bitumens (Orinoco tar and athabasca bitumen).

As for the surfactants usable in the present invention, a nonionicsurfactant having an HLB of from 13 to 19 is suitably used. Further, ananionic surfactant or a cationic surfactant may be preferably added inan amount not exceeding that of the nonionic surfactant in order to givecharges to the particles, and thereby generate repulsive forces betweenthe particles. The "HLB" values in the present invention refer to anabbreviation of a hydrophilic-lipophilic balance calculated from theGriffin's equation. Specifically, the HLB is an index for surfaceactivity by expressing intensity ratios between a hydrophilic propertyand a lipophilic property of a medium which shows both the hydrophilicand lipophilic properties. Here, the found values of Griffin et al. areemployed (W. C. Griffin, "Kirk-Othmer Encyclopedia of ChemicalTechnology," 3rd ed., vol. 8, p.913-916, John-Wiley (1979)).

Examples of the nonionic surfactants usable in the present inventioninclude the following ones:

(i) Alkylene oxide adducts of compounds having phenolic hydroxyl groups,such as phenol, m-cresol, butylphenol, nonylphenol, dinonylphenol,dodecylphenol, p-cumylphenol, and bisphenol A.

(ii) Alkylene oxide adducts of formalin (formaldehyde) condensates ofcompounds having phenolic hydroxyl groups, such as alkylphenols, phenol,m-cresol, styrenated phenol, and benzylated phenol, wherein the averagedegree of condensation is 1.2 to 100, preferably 2 to 20.

(iii) Alkylene oxide adducts of monohydric, aliphatic alcohols and/ormonohydric, aliphatic amines each having 2 to 50 carbon atoms.

(iv) Block or random addition polymers of ethylene oxide/propyleneoxide, ethylene oxide/butylene oxide, ethylene oxide/styrene oxide,ethylene oxide/propylene oxide/butylene oxide, and ethyleneoxide/propylene oxide/styrene oxide.

(v) Alkylene oxide adducts of polyhydric alcohols, such as glycerol,trimethylolpropane, pentaerythritol, sorbitol, sucrose, polyglycerols,ethylene glycol, polyethylene glycols, propylene glycol, andpolypropylene glycols, or esters formed between the above-describedpolyhydric alcohols and fatty acids having 8 to 18 carbon atoms.

(vi) Alkylene oxide adducts of polyvalent amines having a plurality ofactive hydrogen atoms, such as ethylenediamine, tetraethylenediamine,and polyethyleneimine (molecular weight: 600 to 10,000).

(vii) Products formed by addition reaction of alkylene oxides with amixture comprising one mol of fats and oils comprising triglyceride and0.1 to 5 mol of one or more polyhydric alcohols and/or water, thepolyhydric alcohol being selected from the group consisting of glycerol,trimethylolpropane, pentaerythritol, sorbitol, sucrose, ethylene glycol,polyethylene glycols having a molecular weight of 1000 or less,propylene glycol, and polypropylene glycols having a molecular weight of1000 or less.

In each of the nonionic surfactants (i) to (vii), the alkylene oxidemeans, for example, ethylene oxide, propylene oxide, butylene oxide,styrene oxide, and combinations thereof.

Among the above nonionic surfactants, a preference is given those listedin item (i), with a particular preference given to the alkylene oxideadducts of alkylphenols. The nonionic surfactants usable in the presentinvention have an HLB of normally from 13 to 19, preferably from 13.5 to15.5. Although the nonionic surfactants having an HLB of less than 13 orexceeding 19 are also usable, those having HLB values in the range from13 to 19 are preferable from the viewpoint of obtaining stable emulsion.In the present invention, the nonionic surfactants may be used alone orin combination of two or more kinds.

Examples of the anionic surfactants usable in the present inventioninclude the following ones.

(i) Sulfonates of aromatic ring compounds, such asnaphthalenesulfonates, alkylnaphthalenesulfonates,alkylphenolsulfonates, and alkylbenzenesulfonates, or formalin(formaldehyde) condensates of sulfonates of aromatic ring compounds,wherein the average degree of condensation of formalin is 1.2 to 100,and wherein the sulfonates are exemplified by ammonium salts; loweramine salts, such as monoethanolamine salts, diethanolamine salts,triethanolamine salts, and triethylamine salts; and alkali metal saltsor alkaline earth metal salts, such as sodium salts, potassium salts,magnesium salts, and calcium salts.

(ii) Lignin sulfonic acid, salts thereof, or derivatives thereof,formalin (formaldehyde) condensates of lignin sulfonic acid and sulfonicacids of aromatic compounds, such as naphthalenesulfonic acid andalkylnaphthalenesulfonic acids, and salts thereof, wherein the salts forboth the lignin sulfonates and the sulfonates of aromatic compounds areexemplified by ammonium salts; lower amine salts, such asmonoethanolamine salts, diethanolamine salts, triethanolamine salts, andtriethylamine salts; and alkali metal salts or alkaline earth metalsalts, such as sodium salts, potassium salts, magnesium salts, andcalcium salts, and wherein the average degree of condensation offormalin is from 1.2 to 50, preferably from 2 to 50. Among the lignins,excellent performance at high temperatures can be particularly achievedwhen a modified lignin, for instance, those substituted by one or morecarbonyl groups, is used.

(iii) Polystyrenesulfonic acids or salts thereof, copolymers ofstyrenesulfonic acid with other copolymerizable monomer(s), or saltsthereof, wherein the number-average molecular weight is from 500 to500,000, preferably from 2,000 to 100,000, and wherein the salts areexemplified by ammonium salts; lower amine salts, such asmonoethanolamine salts, diethanolamine salts, triethanolamine salts, andtriethylamine salts; and alkali metal salts or alkaline earth metalsalts, such as sodium salts, potassium salts, magnesium salts, andcalcium salts. Here, typical examples of the copolymerizable monomersinclude acrylic acid, methacrylic acid, vinyl acetate, acrylic acidester, olefins, allyl alcohols and ethylene oxide adducts thereof, andacrylamide methylpropylsulfonic acid.

(iv) Polymers of dicyclopentadienesulfonic acid or salts thereof,wherein the number-average molecular weight of the polymers is from 500to 500,000, preferably from 2,000 to 100,000, and wherein the salts areexemplified by ammonium salts; lower amine salts, such asmonoethanolamine salts, diethanolamine salts, triethanolamine salts, andtriethylamine salts; and alkali metal salts or alkaline earth metalsalts, such as sodium salts, potassium salts, magnesium salts, andcalcium salts.

(v) Copolymers of maleic anhydride and/or itaconic anhydride with othercopolymerizable monomer(s), or salts thereof, wherein the number-averagemolecular weight is from 500 to 500,000, preferably from 1,500 to100,000, and wherein the salts are exemplified by ammonium salts; andalkali metal salts, such as sodium salts and potassium salts. Here,typical examples of the copolymerizable monomers include olefins, suchas ethylene, propylene, butylene, pentene, hexene, heptene, octene,nonene, decene, undecene, dodecene, tridecene, tetradecene, pentadecene,and hexadecene, styrene, vinyl acetate, acrylic acid ester, acrylicacid, and methacrylic acid.

(vi) Maleinized liquid polybutadienes or salts thereof, wherein thenumber-average molecular weight of the liquid polybutadienes as thestarting materials is from 500 to 200,000, preferably from 1,000 to50,000, and wherein the degree of maleinization is at a level necessaryfor dissolving the polybutadiene in water, preferably from 40 to 70%,and wherein the salts are exemplified by ammonium salts, and alkalimetal salts, such as sodium salts and potassium salts.

(vii) Anionic surfactants having in the molecule one or two hydrophilicgroups, selected from the group consisting of the following (a) to (h):

(a) Sulfuric acid ester salts of alcohols having 4 to 18 carbon atoms,wherein the salts are exemplified by ammonium salts; lower amine salts,such as monoethanolamine salts, diethanolamine salts, triethanolaminesalts, and triethylamine salts; and alkali metal salts or alkaline earthmetal salts, such as sodium salts, potassium salts, magnesium salts, andcalcium salts. Typical examples thereof include sodium dodecyl sulfateand sodium octyl sulfate.

(b) Alkanesulfonic acids, alkenesulfonic acids, and/or alkylarylsulfonicacids, each having 4 to 18 carbon atoms, or salts thereof, wherein thesalts are exemplified by ammonium salts; lower amine salts, such asmonoethanolamine salts, diethanolamine salts, triethanolamine salts, andtriethylamine salts; and alkali metal salts or alkaline earth metalsalts, such as sodium salts, potassium salts, magnesium salts, andcalcium salts. Typical examples thereof include sodium dodecylbenzenesulfonate, sodium butylnaphthalene sulfonate, and sodium dodecanesulfonate.

(c) Sulfates or phosphates of alkylene oxide adducts of compounds havingin the molecule one or more active hydrogen atoms, or salts thereof,wherein the salts are exemplified by ammonium salts, or alkali metalsalts or alkaline earth metal salts, such as sodium salts, potassiumsalts, magnesium salts, and calcium salts. Typical examples thereofinclude sulfuric acid ester sodium salts of polyoxyethylene(3 mol) nonylphenyl ether, and phosphoric acid ester sodium salts ofpolyoxyethylene(3 mol) dodecyl ether.

(d) Sulfosuccinic acid ester salts of saturated or unsaturated fattyacids having 4 to 22 carbon atoms, wherein the salts are exemplified byammonium salts, and alkali metal salts, such as sodium salts andpotassium salts. Typical examples thereof include sodiumdioctylsulfosuccinate, ammonium dioctylsulfosuccinate, and sodiumdibutylsulfosuccinate.

(e) Alkyldiphenylether disulfonic acids or salts thereof, wherein thealkyl group has 8 to 18 carbon atoms, and wherein the salts areexemplified by ammonium salts, or alkali metal salts or alkaline earthmetal salts, such as sodium salts, potassium salts, magnesium salts, andcalcium salts.

(f) Rosins (or resin acids) or salts thereof, wherein the salts areexemplified by ammonium salts, and alkali metal salts, such as sodiumsalts and potassium salts. Examples thereof include mixed tall acidscomprising a tall rosin and a higher fatty acid, and salts thereof.

(g) Alkanefatty acids or alkenefatty acids each having 4 to 18 carbonatoms, or salts thereof, wherein the salts are exemplified by ammoniumsalts, and alkali metal salts, such as sodium salts and potassium salts.

(h) α-Sulfofatty acid ester salts having an alkyl group of 4 to 22carbon atoms and derivatives thereof, wherein the salts are exemplifiedby ammonium salts, or alkali metal salts or alkaline earth metal salts,such as sodium salts, potassium salts, and magnesium salts.

Among the anionic surfactants listed above, a preference is given to thelignin sulfonates, the formalin condensates of lignin sulfonic acid andnaphthalenesulfonic acid or salts thereof, and the formalin condensatesof naphthalenesulfonates because they show overall superior performancein charging the particles.

The cationic surfactants usable in the present invention are thefollowing ones.

(i) Alkylamine salts and/or alkenylamine salts obtainable byneutralizing an alkylamine or alkenylamine, each having 4 to 18 carbonatoms, with an inorganic acid and/or an organic acid, such ashydrochloric acid and acetic acid.

(ii) Quaternary ammonium salts represented by the following generalformulae (A), (B), and (C): ##STR1## wherein R₁, R₂, R₃, and R₄, whichmay be identical or different, independently stand for an alkyl group oralkenyl group, each having 1 to 18 carbon atoms; and X⁻ stands for acounter anion, including chlorine ion or bromine ion; ##STR2## whereinR₁, R₂, R₃, and X⁻ are as defined above; and ##STR3## wherein R₅ standsfor an alkyl group or alkenyl group having 8 to 18 carbon atoms; R₆stands for a hydrogen atom or a methyl group; and X⁻ is as definedabove.

(iii) Alkylbetaines or alkenylbetaines represented by the followinggeneral formula: ##STR4## wherein R stands for an alkyl group or alkenylgroup, each having 8 to 18 carbon atoms.

(iv) Alkylamine oxides or alkenylamine oxides represented by thefollowing general formula: ##STR5## wherein R is as defined above. (v)Alkylalanines or alkenylalanines represented by the following generalformula: ##STR6## wherein R is as defined above. (vi) Alkylene oxideadduct polymers of diamine or triamine represented by the followinggeneral formula (D) or (E): ##STR7## wherein R is as defined above; andY and Y', which may be identical or different, independently stand foran oxyethylene moiety represented by the general formula: ##STR8##wherein m stands for a number of from 1 to 50. (vii) Polyamine saltsrepresented by the following formula (F) or (G):

    RNHC.sub.3 H.sub.6 NHX'                                    (F)

    RNH(C.sub.3 H.sub.6 NH).sub.2 X'                           (G)

wherein R is as defined above; and X' stands for an inorganic acid ororganic acid, such as hydrochloric acid and acetic acid.

In the present invention, the amount of the nonionic surfactant havingHLB values (hydrophilic-lipophilic balance) ranging from 13 to 19 isfrom 0.1 to 0.6 parts by weight, preferably 0.1 to 0.5 parts by weight,more preferably from 0.2 to 0.4 parts by weight, based on 100 parts byweight of the superheavy oil. When the amount of the nonionic surfactantexceeds 0.6 parts by weight, the particle size of oil droplets shifts toa smaller size, thereby making it impossible to obtain an emulsion ofthe present invention with a desired particle size distribution. On theother hand, when the amount is less than 0.1, the oil droplets becometoo large, thereby making the stability of the resulting emulsion poor.When the oil droplets having particle sizes of 150 μm or more arepresent in large amounts, the emulsion fuel can hardly be subjected to acomplete combustion, a part of which remains incombusted. Therefore, theamount of the coarse particles of 150 μm or more should be preferably aslittle as possible.

In the emulsion fuel of the present invention, the nonionic surfactantsare used as a main component for the surfactant component, and theanionic surfactants and the cationic surfactants may be blended theretoin amounts so as not to impair the inherent properties owned by thenonionic surfactants as mentioned above. By adding the anionicsurfactants and the cationic surfactants, the particles are charged soas to increase the repulsive forces between the emulsion droplets,thereby making the resulting emulsion stable. In the case where thenonionic surfactants are used in combination with the anionicsurfactants or with the cationic surfactants, the total amount of thesurfactants is preferably from 0.1 to 0.6 parts by weight, morepreferably 0.1 to 0.5 parts by weight, based on 100 parts by weight ofthe superheavy oil, as the case where only the nonionic surfactants areused. The amount of the anionic surfactants or the cationic surfactantsis preferably 100 parts by weight or less, more preferably from 5 to 30parts by weight, based on 100 parts by weight of the nonionicsurfactant. The amount of water in the present invention is preferablyfrom 22 to 31 parts by weight, more preferably 22 to 28 parts by weight,based on 100 parts by weight of the superheavy oil.

When polymeric compounds, such as naturally occurring polymers andsynthetic polymers, and water-swellable clay minerals, each of whichbeing exemplified below, are further used to a system using the nonionicsurfactants mentioned above as the surfactant component, since theviscosity at the interface of the liquid droplets is increased, stableemulsified droplets are formed, thereby stabilizing the resultingemulsion. The polymeric compounds usable in the present inventioninclude naturally occurring hydrophilic polymers, such as hydrophilicpolymers derived from naturally occurring substances, and syntheticpolymers. These may be used in an amount so as not to exceed the amountof the nonionic surfactant in step (a).

The hydrophilic polymers derived from naturally occurring substancesincluding microorganisms are one or more substances selected from thegroup consisting of (A) hydrophilic polymers derived from microorganism,(B) hydrophilic polymers derived from plants, (C) hydrophilic polymersderived from animals, and (D) naturally occurring polymer derivativesgiven below. The hydrophilic polymeric substances dissolve or dispersein water, showing high viscosity and gelation.

(A) Hydrophilic Polymers Derived from Microorganism (Polysaccharides)

(a) Xanthan gum

(b) Pullulan

(c) Dextran

(B) Hydrophilic Polymers Derived from Plants (Polysaccharides)

(a) Derived from marine algae:

(i) Agar

(ii) Carrageenan

(iii)Furcellaran

(iv) Alginic acid and salts (Na, K, NH₄, Ca, or Mg) thereof

(b) Derived from seeds:

(i) Locust bean gum

(ii) Guar gum

(iii)Tara gum

(iv) Tamarind gum

(c) Trees (exudates):

(i) Gum arabic

(ii) Gum karaya

(iii)Gum tragacanth

(d) Derived from fruits:

(i) Pectin

(C) Hydrophilic Polymers Derived from Animals (Proteins)

(i) Gelatin

(ii) Casein

(D) Naturally Occurring Polymer Derivatives

(i) Cellulose derivatives, such as carboxymethylcellulose

(ii) Chemically modified starch

The synthetic polymers include the following water-soluble syntheticpolymers given below.

(a) Homopolymers or copolymers of acrylic acid or derivatives thereofrepresented by the following general formula: ##STR9## wherein R' standsfor a hydrogen atom, a methyl group, or an ethyl group; M₁ stands for ahydrogen atom, a sodium ion, a potassium ion, a lithium ion, or anammonium ion; Z₁ stands for a divalent group obtainable bycopolymerizing a monomer represented by the following general formula:##STR10## wherein R' and M₁ are as defined above, and a monomercopolymerizable therewith or salts thereof, wherein the salts of thecopolymerizable monomers are exemplified by ammonium salts, sodiumsalts, potassium salts, and lithium salts; and n stands for a number offrom 50 to 100,000. Examples of monomers copolymerizable with themonomer having the above formula include maleic acid (anhydride),itaconic acid (anhydride), α-olefins, acrylamide, vinylsulfonic acid,allylsulfonic acid, methallylsulfonic acid, andacrylamidomethylpropylsulfonic acid, and salts thereof, includingammonium salts, sodium salts, potassium salts, and lithium salts;dialkyl aminoethyl methacrylates, such as dimethyl aminoethylmethacrylate and diethyl aminoethyl methacrylate and salts thereof,quaternary compounds thereof, including hydrochloric acid, diethylsulfate, and dimethyl sulfate.

(b) Homopolymers or copolymers of acrylamide or derivatives thereofrepresented by the following general formula: ##STR11## wherein R"stands for a hydrogen atom or a C₂ H₄ OH group; Z₂ stands for a divalentgroup obtainable by copolymerizing a monomer represented by thefollowing general formula: ##STR12## wherein R" is as defined above, anda monomer copolymerizable therewith, and salts thereof, wherein thesalts of the copolymerizable monomers are exemplified by ammonium salts,sodium salts, potassium salts, and lithium salts; and n stands for anumber of from 50 to 100,000. Examples of the monomers copolymerizablewith the monomer having the above formula include vinylsulfonic acid,allylsulfonic acid, methallylsulfonic acid,acrylamidomethylpropylsulfonic acid, and salts thereof, includingammonium salts, sodium salts, potassium salts, and lithium salts;dialkyl aminoethyl methacrylates, such as dimethyl aminoethylmethacrylate and dimethyl aminoethyl methacrylate and salts thereof,quaternary compounds thereof, including hydrochloric acid, diethylsulfate, and dimethyl sulfate; styrene; α-olefins having 2 to 18 carbonatoms; and vinylallyl alcohols.

(c) Homopolymers of maleic anhydride or itaconic anhydride, orcopolymers thereof represented by the following general formula:##STR13## wherein M₂ stands for a maleic anhydride unit or itaconicanhydride unit; Z₃ stands for an α-olefin unit, the α-olefins includingethylene, propylene, butylene, isobutylene, octene, decene, anddodecene, or a styrene unit; and n stands for a number of from 50 to100,000.

(d) Polyvinyl alcohols or copolymers thereof represented by thefollowing general formula: ##STR14## wherein Z₄ stands for a vinylacetate unit or styrene unit; and n' stands for a number of from 30 to100,000.

(e) Homopolymers of vinylpyrrolidone, or copolymers thereof representedby the following general formula: ##STR15## wherein Z₅ stands for adivalent group obtainable by copolymerizing a vinylpyrrolidone monomeror salts thereof, wherein the salts of the vinylpyrrolidone includeammonium salts, sodium salts, potassium salts, and lithium salts, and amonomer copolymerizable therewith, and salts thereof, wherein the saltsof the copolymerizable monomers include ammonium salts, sodium salts,potassium salts, and lithium salts. Examples of the monomerscopolymerizable with the vinylpyrrolidone monomer or salts thereofinclude acrylamide, vinylsulfonic acid, methallylsulfonic acid, maleicanhydride, itaconic anhydride, and salts thereof, such as ammoniumsalts, sodium salts, potassium salts, and lithium salts; styrene;a-olefins having 2 to 18 carbon atoms; and n stands for a number of from50 to 100,000.

(f) Polyalkylene oxides having a molecular weight of from 10,000 to5,000,000, wherein the ethylene oxide content is 95% or more, which mayinclude those containing in the molecule 5% or less of various blockpolymers of propylene oxide, butylene oxide, and styrene oxide oralkylaryl groups or alkyl groups.

The water-swellable clay minerals usable in the present inventioninclude the following ones.

The clay minerals usable in the present invention is a highly swellablefine clay mineral, wherein the term "highly swellable" clay mineralsrefer to those bound with a large amount of water molecules when theclay minerals are suspended in water, so as to have a relaxation time(T₂) for water molecules of from 900 msec or less, preferably 500 msecor less, the relaxation time for water molecules being measured by anuclear magnetic resonance spectrometer when the clay minerals aresuspended in water in an amount of 1% by weight on a dry basis. When therelaxation time for the water molecules exceeds 900 msec, the bindingforce of the clay minerals to the water molecules becomes notably weak,to such an extent that the effects of the present invention cannot besufficiently obtained. In addition, the term "fine clay mineral" refersto the clay minerals having an average particle size of from 100 μm orless. When the clay mineral has an average particle size exceeding 100μm, the binding force of the clay minerals to the water moleculesbecomes notably weak, and at the same time sedimentation of the clayminerals is liable to occur, thereby making it impossible tosufficiently attain the effects of the present invention.

Specifically, the fine clay minerals having a high swellability and ahigh binding force to the water molecules, including smectites,vermiculites, and chlorites, fall within the scope of the presentinvention. Among them, however, those having a T₂ value exceeding 900msec are outside the scope of the present invention. Further, sincekaolin produced in Georgia, U.S.A., general kaolin and talc have weakbinding forces to the water molecules, they are excluded from the scopeof the present invention.

The highly swellable fine clay minerals, such as smectites,vermiculites, and chlorites, usable in the present invention will beexplained in detail below.

(A) Smectite has a complicated chemical composition comprising twotetrahedral sheets and one octahedral sheet inserted therebetween(namely a 2:1 layer), because substitution takes place in a wide rangeand various ions accompanied by water molecules are intercalated. Thesmectite is represented by, for example, the following general formula:

    X.sub.m (Y.sup.2+,Y.sup.3+).sub.2-3 Z.sub.4 O.sub.10 (OH).sub.2.nH.sub.2 O,

wherein X stands for K, Na, 1/2Ca, or 1/2Mg; Y²⁺ stands for Mg²⁺, Fe²⁺,Mn²⁺, Ni²⁺, or Zn²⁺, Y³⁺ stands for Al³⁺, Fe³⁺, Mn³⁺, or Cr³⁺ ; and Zstands for Si and/or Al, with proviso that X, Y, and Z stand for anintercalated cation, an octahedral cation, and a tetrahedral cation,respectively.

Typical examples of the smectites are the following ones:

Dioctahedral (octahedral cations being mainly trivalent):

Montmorillonites represented by, for example, the following formula:

    X.sub.0.33 (Al.sub.1.67 Mg.sub.0.33)Si.sub.4 O.sub.10 (OH).sub.2.nH.sub.2 O;

Beidellites represented by, for example, the following formula:

    X.sub.0.33 (Al.sub.2)(Al.sub.0.33 Si.sub.3.67)O.sub.10 (OH).sub.2.nH.sub.2 O; and

Nontronites represented by, for example, the following formula:

    X.sub.0.33 (Fe(III).sub.2)(Al.sub.0.33 Si.sub.3.67)O.sub.10 (OH).sub.2.nH.sub.2 O.

Trioctahedral (octahedral cations being mainly divalent):

Saponites represented by, for example, the following formula:

    X.sub.0.33 (Mg.sub.3)(Al.sub.0.33 Si.sub.3.67)O.sub.10 (OH).sub.2.nH.sub.2 O;

Iron saponites represented by, for example, the following formula:

    X.sub.0.33 (Mg,Fe(II)).sub.3 (Al.sub.0.33 Si.sub.3.67)O.sub.10 (OH).sub.2.nH.sub.2 O;

Hectorites represented by, for example, the following formula:

    X.sub.0.33 (Mg.sub.2.67 Li.sub.0.33)Si.sub.4 O.sub.10 (OH).sub.2.nH.sub.2 O;

Sauconites represented by, for example, the following formula:

    X.sub.0.33 (Mg,Zn).sub.3 (Si.sub.3.67 Al.sub.0.33)O.sub.10 (OH).sub.2.nH.sub.2 O; and

Stevensites represented by, for example, the following formula:

    X.sub.0.33/2 (Mg.sub.2.97)Si.sub.4 O.sub.10 (OH).sub.2.nH.sub.2 O.

Among the smectites listed above, the montmorillonites, the beidellites,and the nontronites constitute a series which can be subjected toisomorphous substitution. The stevensites have layer charges of one-halfof that of the other smectites, and thus having an intermediary propertyof the dioctahedral smectites and the trioctahedral smectites.

(B) Vermiculites pertain to 2:1 layer silicates and are represented by,for example, the following formula:

    (Mg,Fe(III),Al).sub.2-3 (Si.sub.4-x Al.sub.x)O.sub.10 (OH).sub.2 (M.sup.+,M.sup.2+.sub.1/2).sub.x.nH.sub.2 O.

In the above formula, M stands for an intercalated exchangeable cation,and when the vermiculite is in the form of coarse particles, M is mainlycomposed of Mg. "n" in the above formula stands for the amount of water,and when the intercalated cation is Mg, water forms a bimolecular layerover a wide temperature range and n is in the range of from about 3.5 to5. "x" in the above formula stands for layer charges which are in therange of from 0.6 to 0.9.

In the above formula, it is assumed that all of the layer charges aregenerated by the substitution of tetrahedral cations. However, incertain cases, the octahedral sheet may actually carry a negative chargeto which the layer charges are ascribed. The number of octahedralcations is 2 to 3, and the vermiculites are classified into dioctahedralvermiculites and trioctahedral vermiculites. The vermiculites in theform of coarse particles obtainable by the weathering of biotite andphlogopite are trioctahedral vermiculites.

(C) The structures of the chlorites are similar to those of thesmectites and the vermiculites, and the base plane interval is 14 to 15Å. The chlorites are typically a 2:1 hydrated silicate which can beclassified into trioctahedral chlorites and dioctahedral chloritesdepending on the properties of the 2:1 layer.

The trioctahedral chlorites are represented by, for example, thefollowing formula:

    (R.sub.6-x.sup.2+ R.sub.x.sup.3+)(Si.sub.4-x Al.sub.x)O.sub.10 (OH).sub.8.

In the above formula, R²⁺ is mainly composed of Mg and Fe²⁺, which mayalso include Mn²⁺ and Ni²⁺ ; and R³⁺ is mainly composed of Al, which mayalso include Fe³⁺ and Cr³⁺. "x" in the above formula is a value of from0.8 to 1.6.

A chlorite wherein R²⁺ is mainly composed of Mg is so-called"clinochlore" e.g. (Mg₅ Al)(Si₃ Al)O₁₀ (OH)₈ !; and a chlorite whereinR²⁺ is mainly composed of Fe(II) is so-called "chamosite" e.g. (Fe₅Al)(Si₃ Al)O₁₀ (OH)₈ !. Examples of other trioctahedral chloritesinclude "pennantite" wherein R²⁺ is mainly composed of Mn(II); and"unimite" wherein R²⁺ is mainly composed of Ni(II).

The dioctahedral chlorites wherein the octahedral cation is mainlycomposed of Al are classified into the following three kinds.

Sudoite e.g. (Mg,Al)₄.6-5 (Si,Al)₄ O₁₀ (OH)₈ ;

Cookeite e.g. (LiAl₄)(Si₃ Al)O₁₀ (OH)₈ ; and

Donbassite e.g. Al₄₋₄.2 R₀.2 (Si,Al)₄ O₁₀ (OH)₈.

The clay minerals comprising montmorillonite, the clay mineralpertaining to smectite, as the main component, and further containing asimpurities, quartz, α-cristobalite, opal, feldspar, mica, zeolite,calcite, dolomite, gypsum, and iron oxide are so-called "bentonite." Thebentonites include sodium bentonite rich in Na ions and calciumbentonite rich in Ca ions. Since sodium bentonite has high swellability,it falls within the scope of the clay minerals of the present invention,while calcium bentonite has notably low swellability that it is excludedfrom the scope of the present invention.

Among the sodium bentonites, those having a higher content of themontmorillonites are preferred. Also, the particle size is preferably100 μm or less, more preferably 10 μm or less. The sodium bentonitesfalling within the scope of the clay minerals of the present inventionshould have a relaxation time (T₂) for water molecules of from 900 msecor less, preferably 500 msec or less, the relaxation time for watermolecules being measured by a nuclear magnetic resonance spectrometerwhen the clay minerals are suspended in water in an amount of 1% byweight on a dry basis.

In the sodium bentonites, impurities contained therein and differencesin swellability depend upon the place of origin. When themontmorillonite content in the sodium bentonites is increased byelutriation or other means, the T₂ value of the aqueous suspension ofthe resulting sodium bentonite becomes low, thereby more fully enhancingthe effects of the present invention.

The above polymeric compounds and the clay minerals may be used alone orin combination of two or more. The polymeric compounds and clay mineralsmay be preferably added so as not to exceed the amount of the nonionicsurfactant used. Specifically, the amount of the polymeric compounds orclay minerals is preferably from 2 to 40 parts by weight, morepreferably from 4 to 20 parts by weight, based on 100 parts by weight ofthe nonionic surfactant. The polymeric compounds or clay minerals may beadded while preparing a homogeneous liquid mixture formed by emulsifyingsuperheavy oil in water using a nonionic surfactant, or they mayalternatively added after preparing the homogeneous liquid mixture. Whenthe polymeric compounds or clay minerals are added to a surfactantcomponent comprising a nonionic surfactant and an anionic surfactant ora cationic surfactant, the effects for adding the polymeric compounds orthe clay minerals are notably exhibited. In this case, the polymericcompounds and the clay minerals may be used in combination.

When the liquid mixture is prepared by emulsifying a superheavy oil witha nonionic surfactant, oxides of magnesium, calcium, or iron, hydroxidesof magnesium, calcium, or iron, salts, such as nitrates and acetates, ofmagnesium, calcium, or iron may be added. By adding oxides, hydroxides,or salts, the emulsification stability effect can be obtained. In thecase where the oxides or hydroxides are added, the amount thereof isfrom 0.01 to 0.5 parts by weight, preferably from 0.02 to 0.08 parts byweight, based on 100 parts by weight of the superheavy oil.

The method for producing the superheavy oil emulsion fuel of the presentinvention comprises the steps of:

(a) adding to a superheavy oil 0.1 to 0.6 parts by weight of a nonionicsurfactant having an HLB (hydrophilic-lipophilic balance) of 13 to 19,based on 100 parts by weight of the superheavy oil, and water, toprepare a homogeneous liquid mixture; and

(b) mechanically mixing the homogeneous liquid mixture with a highshearing stress.

In the case where the emulsion has a high viscosity, a step (c) ofdiluting the resulting mixture obtained in step (b) with water or watercontaining additives, such as surfactants having an HLB of 13 to 19 maybe further provided subsequent to step (b), to prepare an emulsion fuelhaving a high fluidity. Especially, the viscosity (100 s⁻¹, 25° C.) ofthe resulting mixture may be adjusted to 3000 cp or less. In theresulting emulsion fuel of the present invention, the concentration ofthe superheavy oil in the emulsion fuel is from 76.5 to 82.0% by weight,preferably from 78.0 to 81.0% by weight, more preferably 78.0 to 81.0%by weight, and the emulsion has a suitable particle size distribution ina given range.

The emulsion fuel obtainable by the method of the present invention hasa particle size distribution wherein a 10%-cumulative particle size isfrom 1.5 to 8 μm, a 50%-cumulative particle size is from 11 to 30 μm,preferably 15 to 20 μm, and a 90%-cumulative particle size is from 25 to150 μm, and wherein coarse particles having particle sizes of 150 μm ormore occupy 3% by weight or less in the entire emulsion fuel.Incidentally, the term "particle size" used herein refers to particlediameter. The "particle size" and "amount of coarse particles" areevaluated by methods explained in Examples which are set forthhereinbelow.

FIG. 1 is a graph showing a particle size distribution of an emulsionfuel obtained in Example 1 set forth below; and FIG. 2 is a graphshowing a particle size distribution of an emulsion fuel obtained inComparative Example 1. The emulsion fuels shown in FIGS. 1 and 2 areproduced under the same conditions except for changing the amounts ofthe nonionic surfactant. The particle size distribution of the inventiveproduct shown in FIG. 1 is such that a 10%-cumulative particle size is3.1 μm, a 50%-cumulative particle size is 17.4 μm, and a 90%-cumulativeparticle size is 58.1 μm, and wherein coarse particles having particlesizes of 150 μm or more occupy 1.0% by weight in the entire emulsionfuel. On the other hand, the particle size distribution of thecomparative product shown in FIG. 2 is such that a 10%-cumulativeparticle size is 1.7 μm, a 50%-cumulative particle size is 8.6 μm, and a90%-cumulative particle size is 30.0 μm, and wherein coarse particleshaving particle sizes of 150 μm or more occupy 0% in the entireemulsion.

The method of the present invention is characterized in that thesuperheavy oil emulsion fuel is produced by limiting the amount of thesurfactants having the nonionic surfactants mentioned above as a maincomponent to 0.1 to 0.6 parts by weight, preferably 0.1 to 0.5 parts byweight, based on 100 parts by weight of the superheavy oil, and that ahigh shearing stress is applied upon mechanical mixing, to produce anemulsion fuel having the particle size distribution specified as aboveand having a concentration of the superheavy oil of from 76.5 to 82.0%by weight, preferably from 78.0 to 81.0% by weight. The resultingemulsion fuel has a high superheavy oil concentration, good fluidity,with easy handling and conveying.

The agitators to be used for pre-mixing in the present invention are notparticularly required to have a high shearing stress, and any one ofgeneral agitators, such as propeller agitators, will suffice. Theagitation after the pre-mixing is preferably carried out by highshearing stress agitators. Examples thereof include line mixers, arrowblade turbine blade mixers, propeller blade mixers, full margin-typeblade mixers, paddle blade mixers, high-shearing turbine mixers,homogenizers, and colloidal mills. Here, the term "high shearing stress"refers to a shearing stress of 1,000 to 20,000 sec⁻¹, more preferably4,000 to 20,000 sec⁻¹.

When the concentration of the superheavy oil exceeds 80% by weight, theviscosity of the emulsion composition becomes too high. Therefore, afterthe mechanical mixing by shearing force as mentioned above, when theemulsion having too high superheavy oil concentration is further dilutedwith water or an aqueous solution containing a surfactant having HLB of13 to 19, and then agitated so as to give an emulsion fuel with asuperheavy oil concentration of from 77 to 79% by weight, the viscosityis also lowered to 3000 c.p. or less, preferably 2000 c.p. or less,particularly from 300 to 1000 c.p. (100 sec⁻¹, 25° C.), therebyproducing stable emulsion.

The present invention will be further described by means of thefollowing working examples and comparative examples, without intendingto restrict the scope of the present invention thereto.

EXAMPLES 1 to 15 AND COMPARATIVE EXAMPLES 1 TO 4

Given amounts of water and asphalt ("STRAIGHT ASPHALT," according to JISK-2207, manufactured by Cosmo Oil Co.; penetration: 80 to 100), and asurfactant and/or a stabilizer shown in Tables 1 to 3 were placed in a800 ml-stainless steel container, and the contents were heated to agiven temperature in a thermostat, and the mixture in the container waspre-mixed using an agitator equipped with double, helical ribbon bladesfor 5 minutes at a rotational speed of 60 r.p.m. Thereafter, theresulting mixture was blended and emulsified using a "T.K. HOMO MIXER,Model M" (equipped with low-viscosity agitating blades; manufactured byTokushu Kika Kogyo) to produce an emulsion fuel under the followingconditions.

The production conditions are as follows. Agitation rotational speed:8000 r.p.m.; agitation time: 2 minutes; temperature: 80° C.; shearingstress: 12000/sec. Here, the specific gravity of water is 0.997 (25°C.), and the specific gravity of oil is 1.026 (25° C.). The viscositywas measured by using a double, cylindrical rotational viscometer "RV-2"(equipped with a sensor "MV-1," manufactured by Haake Co.) at 25° C.while applying a shearing stress of 100/sec.

The particle size of the obtained emulsion fuel was evaluated by using agranulometer "HR850-B" (manufactured by Cyrus Co.) to determine10%-cumulative particle size (average particle diameter), 50%-cumulativeparticle size (average particle diameter), and 90%-cumulative particlesize (average particle diameter).

Specifically, the particle size was evaluated by the following method.Several droplets of the emulsion fuel were added in an aqueous solutioncontaining 0.3% by weight of a nonionic surfactant (polyoxyethylene(20mol) nonyl phenyl ether), and the resulting mixture was agitated using astirrer to provide a homogeneous liquid mixture. The homogeneous liquidmixture obtained above was placed in a granulometer to evaluategranularity. The measurement mode was set at 1 to 600 μm.

The amount of coarse particles was evaluated by measuring the componentshaving particle sizes of 150 μm or more using a wet sieve. Specifically,20 g of each the emulsion fuels was weighed and then poured on thesieve. After rinsing the mesh-on particles with water, they were driedwith a vacuum dryer. The amount of the particles remaining on the sieveafter drying was measured to calculate the amount of coarse particles.Also, emulsion stabilities after one day, after one week, and after onemonth were evaluated by the amount of sediments. Further, the overallevaluation was conducted by collectively evaluating the viscosity of theemulsion fuels, the particle sizes at 10% accumulation, 50%accumulation, and 90% accumulation, the percentage of coarse particles,and the emulsion stability, as determined by the following standards:

⊚: Very excellent;

∘: Good;

Δ: Slight effect; and

x: No effects.

                                      TABLE 1    __________________________________________________________________________                             Conc. of                             Super-                                  Particle Size    Exam-                    heavy                                  (μm)  Coarse                                                Emulsion Stability                                                               Overall    ple                 Viscosity                             Oil  10%                                     50%                                        90%                                           Particles                                                After                                                     After                                                          After                                                               Evalu-    Nos.        Surfactant and Stabilizer                     HLB                        (c.p.)                             (wt %)                                  Cum.                                     Cum.                                        Cum.                                           (wt %)                                                One Day                                                     One Week                                                          One                                                               ation    __________________________________________________________________________    1   Polyoxyethylene                0.30 wt %                     14.4                        >3000                             81.1 3.1                                     17.4                                        58.1                                           1.0  Creamy                                                     Creamy                                                          Creamy                                                               ◯        nonyl phenyl        ether    2   Polyoxyethylene                0.30 wt %                     14.4                          2193                             79.6 2.8                                     14.4                                        55.0                                           1.6  Excel.                                                     Slightly                                                          Soft .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Soft Sediment        ether                                   fication                                                     Sediment    3   Polyoxyethylene                0.30 wt %                     14.4                           187                             77.6 2.0                                     13.4                                        42.1                                           1.8  Excel.                                                     Slightly                                                          Soft .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Soft Sediment        ether                                   fication                                                     Sediment    4   Polyoxyethylene                0.30 wt %                     14.4                           169                             77.1 1.6                                     12.8                                        30.0                                           2.2  Excel.                                                     Soft Soft ◯        nonyl phenyl                            Emulsi-                                                     Sediment                                                          Sediment        ether                                   fication    5   Polyoxyethylene                0.30 wt %                     14.4                           148                             76.5 1.5                                     12.2                                        25.0                                           2.9  Excel.                                                     Soft Soft ◯        nonyl phenyl                            Emulsi-                                                     Sediment                                                          Sediment        ether                                   fication    6   Polyoxyethylene                0.30 wt %                     16.0                          2350                             79.7 2.5                                     13.5                                        49.0                                           1.7  Excel.                                                     Slightly                                                          Soft .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Soft Sediment        ether                                   fication                                                     Sediment    7   Polyoxyethylene                0.30 wt %                     17.1                          2911                             79.8 1.5                                     12.9                                        40.1                                           2.0  Excel.                                                     Slightly                                                          Soft .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Soft Sediment        ether                                   fication                                                     Sediment    8   Polyoxyethylene                0.30 wt %                     13.3                          2615                             79.7 1.7                                     14.0                                        47.0                                           1.8  Excel.                                                     Slightly                                                          Soft .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Soft Sediment        ether                                   fication                                                     Sediment    __________________________________________________________________________

                                      TABLE 2    __________________________________________________________________________                             Conc. of                             Super-                                  Particle Size    Exam-                    heavy                                  (μm)  Coarse                                                Emulsion Stability                                                               Overall    ple                 Viscosity                             Oil  10%                                     50%                                        90%                                           Particles                                                After                                                     After                                                          After                                                               Evalu-    Nos.        Surfactant and Stabilizer                     HLB                        (c.p.)                             (wt %)                                  Cum.                                     Cum.                                        Cum.                                           (wt %)                                                One Day                                                     One Week                                                          One                                                               ation    __________________________________________________________________________     9  Polyoxyethylene                0.30 wt %                     14.4                        2438 79.8 2.1                                     14.4                                        41.2                                           1.9  Excel.                                                     Slightly                                                          Soft .circleincircle                                                               .        oleyl ether                             Emulsi-                                                     Soft Sediment                                                fication                                                     Sediment    10  Polyoxyethylene                0.24 wt %                     14.4                        1524 79.5 3.0                                     16.5                                        53.4                                           1.9  Excel.                                                     Slightly                                                          Soft .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Soft Sediment        ether                                   fication                                                     Sediment        Sodium lignin                0.06 wt %        sulfonate    11  Polyoxyethylene                0.24 wt %                     14.4                        1852 78.4 2.6                                     15.2                                        56.1                                           1.4  Excel.                                                     Excel.                                                          Slightly                                                               .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Emulsi-                                                          Soft        ether                                   fication                                                     fication                                                          Sediment        Sodium lignin                0.05 wt %        sulfonate        Xanthan gum                0.01 wt %    12  Polyoxyethylene                0.24 wt %                     14.4                        1913 78.2 2.4                                     14.9                                        55.6                                           1.4  Excel.                                                     Excel.                                                          Slightly                                                               .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Emulsi-                                                          Soft        ether                                   fication                                                     fication                                                          Sediment        Sodium lignin                0.03 wt %        sulfonate        Hydroxyethyl                0.03 wt %        cellulose    13  Polyoxyethylene                0.24 wt %                     14.4                        1996 78.0 2.4                                     14.5                                        55.2                                           1.5  Excel.                                                     Excel.                                                          Slightly                                                               .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Emulsi-                                                          Soft        ether                                   fication                                                     fication                                                          Sediment        Sodium lignin                0.03 wt %        sulfonate        Water-swellable                0.03 wt %        Montmorillonite    __________________________________________________________________________

                                      TABLE 3    __________________________________________________________________________                             Conc. of                             Super-                                  Particle Size                             heavy                                  (μm)  Coarse                                                Emulsion Stability                                                               Overall                        Viscosity                             Oil  10%                                     50%                                        90%                                           Particles                                                After                                                     After                                                          After                                                               Evalu-    Nos.        Surfactant and Stabilizer                     HLB                        (c.p.)                             (wt %)                                  Cum.                                     Cum.                                        Cum.                                           (wt %)                                                One Day                                                     One Week                                                          One                                                               ation    __________________________________________________________________________    Example Nos.    14*.sup.1        Polyoxyethylene                0.30 wt %                     14.4                        180  77.5 3.0                                     17.0                                        57.5                                           0.3  Excel.                                                     Excel.                                                          Slightly                                                               .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Emulsi-                                                          Soft        ether                                   fication                                                     fication                                                          Sediment    15*.sup.2        Polyoxyethylene                0.30 wt %                     14.4                        194  77.7 2.5                                     14.1                                        54.0                                           1.0  Excel.                                                     Excel.                                                          Slightly                                                               .circleincircle                                                               .        nonyl phenyl                            Emulsi-                                                     Emulsi-                                                          Soft        ether                                   fication                                                     fication                                                          Sediment    Comparative Example Nos.     1  Polyoxyethylene                0.60 wt %                     14.4                        --*.sup.1                             81.1 1.7                                      8.6                                        30.0                                           0    No Free                                                     No Free                                                          No                                                               Xree        nonyl phenyl                            Flowing                                                     Flowing                                                          Flowing        ether     2  Polyoxyethylene                0.30 wt %                     14.4                        122  75.4 1.4                                      6.8                                        23.4                                           3.5  Slightly                                                     Soft Soft Δ        nonyl phenyl                            Soft Sediment                                                          Sediment        ether                                   Sediment     3  Polyoxyethylene                0.30 wt %                     14.4                        103  73.4 1.3                                      5.3                                        23.0                                           4.2  Slightly                                                     Soft Soft Δ        nonyl phenyl                            Soft Sediment                                                          Sediment        ether                                   Sediment     4  Polyoxyethylene                0.12 wt %                     14.4                        --*.sup.3                             79.6 --*.sup.3                                     --*.sup.3                                        --*.sup.3                                           52.3 Tar  Separation                                                          Separation                                                               X        nonyl phenyl                            Sediment        ether        Sodium lignin                0.18 wt %        sulfonate    __________________________________________________________________________     Notes after Table 3:     *.sup.1 : An emulsion fuel prepared by diluting the emulsion fuel obtaine     in Example 1 with an aqueous solution of 0.30% by weightpolyoxyethylene     (13 mol) nonyl phenyl ether to a given concentration, and then blending     the resulting mixture at a high shearing stress in the same manner as in     Example 1.     *.sup.2 : An emulsion fuel prepared by diluting the emulsion fuel obtaine     in Example 2 with an aqueous solution of 0.30% by weightpolyoxyethylene     (13 mol) nonyl phenyl ether to a given concentration, and then blending     the resulting mixture at a high shearing stress in the same manner as in     Example 1.     *.sup.3 : Nondetectable.

As is clear from Tables 1 to 3, the emulsion fuels obtained according tothe method of the present invention had high superheavy oilconcentrations and excellent emulsion stability. By contrast, theemulsion fuels obtained in Comparative Examples had low superheavy oilconcentrations, or had poor emulsion stability even at high superheavyoil concentrations.

INDUSTRIAL APPLICABILITY

According to the method of the present invention, a stable,easy-to-handle superheavy oil emulsion fuel having high superheavy oilconcentration and good fluidity can be easily produced.

The present invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

We claim:
 1. A method for producing a superheavy oil emulsion fuelcomprising the steps of:(a) adding to a superheavy oil 0.1 to 0.6 partsby weight of a nonionic surfactant having an HLB (hydrophilic-lipophilicbalance) of 13 to 19, based on 100 parts by weight of the superheavyoil, and water, to prepare a homogeneous liquid mixture, whereinoptionally an anionic surfactant or a cationic surfactant is furtheradded provided that the total amount of said nonionic surfactant andsaid anionic surfactant on the total amount of said nonionic surfactantand said cationic surfactant is from 0.1 to 0.6 parts by weight, basedon 100 parts by weight of the superheavy oil, and that the amount ofsaid anionic surfactant or said cationic surfactant is 100 parts byweight or less, based on 100 parts by weight of the nonionic surfactant;and (b) mechanically mixing the homogeneous liquid mixture with a highshearing stress, to produce a superheavy oil emulsion fuel having aparticle size distribution wherein a 10%-cumulative particle size isfrom 1.5 to 8 μm, a 50%-cumulative particle size is from 11 to 30 μm,and a 90%-cumulative particle size is from 25 to 150 μm, and whereincoarse particles having particle sizes of 150 μm or more occupy 3% byweight or less in the entire emulsion fuel, and wherein theconcentration of the superheavy oil is from 76.5 to 82.0% by weight. 2.The method according to claim 1, wherein a polymeric compound selectedfrom the group consisting of naturally occurring polymers and syntheticpolymers, or a water-swellable clay mineral is further added in anamount so as not to exceed the amount of the nonionic surfactant in step(a).
 3. The method according to claim 1, or wherein one or morecompounds selected from the group consisting of oxides of magnesium,calcium, and iron, hydroxides of magnesium, calcium, and iron, and saltsof magnesium, calcium, and iron are further added in an amount of 0.01to 0.5 parts by weight, based on 100 parts by weight of the superheavyoil in step (a).
 4. The method according to any one of claims 1 to 3,wherein the mechanical mixing is carried out at a shearing stress offrom 1,000 to 20,000 s⁻¹.
 5. The method according to any one of claims 1to 3, subsequent to step (b), further comprising the step of:(c)diluting the resulting mixture obtained in step (b) with water or watercontaining a surfactant having an HLB of 13 to 19, to thereby adjust theviscosity (100 s⁻¹, 25° C.) of the resulting mixture to 3000 cp or less.6. The method according to any one of claims 1 to 3, wherein theconcentration of the superheavy oil is from 78.0 to 81.0% by weight. 7.The method according to any one of claims 1 to 3, wherein said nonionicsurfactant is an alkylene oxide adduct of an alkylphenol.
 8. The methodaccording to claim 1, wherein said anionic surfactant is one or morecompounds selected from the group consisting of lignin sulfonates,formalin condensates of lignin sulfonic acid and naphthalenesulfonicacid or salts thereof, and formalin condensates ofnaphthalenesulfonates.